SPRINGFIELD — With just hours left before Massachusetts voters weigh in on the 2016 presidential primary contests, Democratic rivals Hillary Clinton and Bernie Sanders remain in a dead heat, a new poll has found.

A UMass Amherst / WBZ survey released late Monday found the former secretary of state and Vermont senator essentially tied with a respective 44 and 43 percent of the vote among likely Massachusetts primary voters.

While Democrats remain largely split over their party's candidates, Massachusetts Republicans overwhelmingly support businessman Donald Trump, who has tripled his lead over other GOP hopefuls, according to the poll results.

Although Clinton, who campaigned across the state Monday, is neck-and-neck with Sanders, her lead increases slightly to 47 percent when including responses from voters who said they are "leaning" toward supporting her, the poll found. Sanders, who also stopped in the Bay State on Monday, saw support increase to just 44 percent when including leaners.

Brian Schaffner, director of the UMass Amherst / WBZ Poll, called Massachusetts "a bellwether state for determining whether Sanders has staying power in this race.

"If he can't succeed here, then there aren't too many other states he can count on winning," Schaffner said, pointing to Massachusetts' demographics.

Sanders holds a 48 to 42 percent lead among men and 58 to 36 lead among voters aged 29 and younger, according to the survey. Clinton, meanwhile, holds a 50 to 41 percent lead among women and 56 to 42 percent lead among voters aged 30 to 44.

While the Democratic candidates are largely tied, nearly two-thirds of voters said they believe Clinton is most likely to win the Democratic Party's nomination.

On the other side of the race, Trump is poised to see a big victory in Massachusetts on "Super Tuesday."

Forty-six percent of likely Republican primary voters said they would back the businessman, compared to just 14 percent who would respectively support U.S. Sens. Marco Rubio, R-Fla., and Ted Cruz, R-Texas.

About two-thirds of GOP voters, regardless of whom they support, meanwhile, said they believe Trump will win the party's nomination.

"Massachusetts Republicans are not like the rest of the GOP, but the popularity of Trump's positions are in such contrast to conventional GOP doctrine that the party leaders must be thinking 'counter-reformation' at this point, even if Trump does not get the nomination," said Ray La Raja, associate director of the UMass Amherst / WBZ Poll.

The poll, which surveyed nearly 900 likely Massachusetts primary voters, was conducted from Feb. 19 to 25 by YouGov. It has a margin of error of plus or minus 6.3 percent among Republican likely voters and 6.5 percent among likely Democratic voters.